Soil Vapor Extraction | Technology Description

Soil Vapor Extraction (SVE) is an in-situ remediation technology used to remediate soils impacted with volatile organic compounds (VOCs) including gasoline and chlorinated hydrocarbons. This technology works by installing wells and using blowers to induce a vacuum and extract vapors from the subsurface. The vadose zone is remediated through the following mechanisms: (1) capture of soil gas in the vadose zone; (2) pneumatic control of soil gas and VOCs beyond the area targeted for remediation; (3) volatilizing of free product, and; (4) desorption of VOCs in soil. The soil vapor extracted from the subsurface is conveyed to an air emissions control systems to remove the VOCs prior to atmospheric discharge. The design, construction, and operation of SVE systems require permitting and operation in compliance with air emissions regulations.

During remediation with SVE, a blower is used to induce a vacuum and the vacuum is applied to the subsurface through a network of vertical SVE wells installed to the depth of concern. The soil vapor impacted with VOCs is routed to above grade equipment for air emissions control.

SVE System Design

We implement proven designs into our SVE systems for ongoing process optimization and to shorten the site remediation timeframe. These proven designs allow us to obtain regulatory closure on chemically impacted sites.

SVE System Installation

SVE well locations are selected to create a capture zone that extends beyond the VOC plume boundaries. To optimize the well configuration, a numerical airflow models can be used to simulate subsurface airflow conditions. The final SVE system designs generally include multi-depth extraction well networks and SVE and emission control systems. SVE air emission control systems are selected based on the type of contaminant and concentrations. We have used thermal oxidizers, catalytic oxidizers, vapor phase granular activated carbon (VPGAC), and rotary thermal oxidizers (RTOs).

SVE System Operation and Maintenance

Operation activities include the following: (1) monitoring system pressures, air flows, and temperature; (2) estimating VOC mass removal rates; (3) PID monitoring and sampling of inlets and outlets to monitor compliance with air emissions permits; and (4) monitoring and maintenance of process equipment, including mechanical and electrical. Quarterly operations reports are prepared to document the remediation progress and used to update regulators and gather data for eventual regulatory closure.

Process Optimization

SVE wells and systems are designed for to continuously optimize systems. The SVE system configuration and piping at the manifolds are designed to operate those SVE wells with high VOC mass removal rates, and close SVE wells with low VOC mass removal. The optimization process in combination with the rebound and soil vapor data were used to induce variable subsurface air flow dynamics for enhanced remediation of recalcitrant areas.

Regulatory Support

Regulatory support is provided throughout the process by providing regulatory support with the lead regulator, preparing remedial action plans, sampling action plans, and operations and maintenance reports.